Europe ..." (11). Recent evidence suggests that, in Latin America a the acceleration of reduction in mortality has been even greater than supposed (12). Furthermore, the levels of mortality in Latin America and other p the developing world were higher than those in western Europe wh latter began its modern demographic transition. The evidence for Latin ica and other parts of the world suggests that acceleration in mortality tion has been to some extent independent of economic development, presumably related to the introduction of cheap public health and r technology. Paralleling the established facts about mortality decline is the cc assumption that natality changes will occur gradually, perhaps more 1 European experience. In western Europe, the transition took 50 y more, often commencing from much lower levels of natality than tho prevailing in most of the less developed world. The available evidence does not support this assumption. Rather th been an acceleration in the rate at which countries move through the graphic transition from high to low birth rates. This proposition is < strated in Table 2, in which are compared the reductions of the bii now occurring in less developed countries and those that occurred it TABLE 2 Years Historically and Currently Required for Countries to Reduce Annual Ci Birth Rates from 35 to 20, 1875 to circa 1969a Period in Which Birth Rate Reached 35 or Below Number of Countries Number of Years Reqt to Reach Birth Rate o Mean Median 1875-99 9 48 50 1900-24 7 38 32 1925-49 5u 31 28 1950- 6b 15 14 aThe following countries are included: 1875-99-Austria, Australia, Engl Wales, Finland, Italy, Netherlands, New Zealand, Scotland, United States; 1 Argentina, Czechoslovakia, Germany, Hungary, Japan, Portugal, Spain; 1 Bulgaria, Poland, Rumania, the Soviet Union, Yugoslavia; 1950- -Ceylon, Chi Kong, Puerto Rico, Singapore, Taiwan. The initial and terminal dates were dc by 3-year averages rounded to 35 and 20 respectively and bracketing continued ward trend in the birth rate. A number of European countries were not included their birth rates were already below 35 in 1875. bNonc of these countries have yet reached a birth rate of 20. The average am cent decline in the birth rate since reaching a crude birth rate of 35 was in c extrapolated to estimate the total years required to pass from 35 to 20.women passing through their reproductive years, is the final and most accurate measure of fertility, but it docs not measure recent change, which is precisely what we are after here. One cannot get around the basic fact that women have births at changing intervals and over a long period of time. A woman at age 45, who has completed her childbearing, usually had her first child 20 to 30 years previously and her number of children reflectstions.